Background of the Invention
[0001] This invention relates to voltage reference circuits, and more particularly, to a
bandgap voltage reference circuit for providing a stable output voltage operating
independent of temperature and power supply variations.
[0002] Voltage reference circuits are common in many modern electronic designs for providing
a stable reference signal. The bandgap voltage reference circuit is well suited for
this niche due to its temperature independent characteristics as discussed in an article
entitled "A SIMPLE THREE-TERMINAL IC BANDGAP REFERENCE" by A. Paul Brokaw, IEEE Journal
of Solid State Circuits, Vol. SC-9, No. 6, December, 1974. Briefly, the Brokaw article
discloses a two transistor configuration conducting equal currents, but having dissimilar
emitter areas, say eight-to-one, creating different current densities and base-emitter
junction potentials (V
be). The first transistor typically possesses the larger emitter area and, correspondingly,
the lower current density and the lesser V
be. By connecting two resistors in series with the emitter path of the first transistor
and coupling the emitter of the second transistor to the interconnection thereof,
a delta V
be having a positive temperature coefficient is developed across the upper resistor.
If the currents flowing through the first and second transistors are made of appropriate
and constant magnitude and equal in value, the positive temperature coefficient of
the voltage across the upper resistor tends to cancel the inherent negative temperature
coefficient of the base-emitter junction of the first transistor thereby providing
an output voltage at the collector of the second transistor which is insensitive to
temperature variation, as is understood.
[0003] The current flowing through the first and second transistors is typically provided
by a PNP transistor current mirror configuration having the emitters thereof coupled
to the positive power supply conductor. Any transients appearing on the positive power
supply are reflected in the current flowing through the first and second transistors,
inducing variation in the V
be's thereof and the potential developed across the emitter resistors. This translates
to movement in the collector potential of the second transistor, thus, the output
voltage is dependent upon the power supply voltage. The fluctuation in the circuit
signal levels attributed to power supply variation is commonly known as the Early
voltage effect and is an undesirable condition which adversely influences the regulated
output signal.
[0004] One known bandgap voltage reference circuit that operates independent of power supply
variation is disclosed in International Patent Application WO-A 85/02472. Another
known bandgap voltage reference circuit that operates independent of power supply
variation with all NPN transistors is disclosed in U.S. Patent 4,628,248. Yet another
known voltage reference circuit that allows control over the magnitude and temperature
coefficient of the output voltage by using a precision thermal current source is disclosed
in European Patent Application EP-A-0,264,563.
[0005] There is, however, a need for an improved voltage reference circuit having an output
voltage operating independent of temperature and power supply variations.
Summary of the Invention
[0006] Accordingly, an objective of the present invention is to provide an improved voltage
reference circuit.
[0007] In accordance with the above and other objectives there is provided a voltage reference
circuit for providing a voltage at an output, comprising:
current supply means including an output for supplying a current having a predetermined
temperature coefficient;
a first transistor having a collector, a base and an emitter, said collector being
coupled for receiving said current having said selectable temperature coefficient
from said output of said current supply means, said base being coupled to the output
of the voltage reference circuit, said first transistor having a temperature coefficient
across the base-emitter junction thereof;
circuit means coupled between said collector and base of said first transistor for
supplying base drive thereto; and
a first resistor coupled between said emitter of said first transistor and a first
source of operating potential for conducting said current having said predetermined
temperature coefficient which develops a potential across said first resistor with
a temperature coefficient opposing said temperature coefficient across the base-emitter
junction of said first transistor.
[0008] In another aspect, the present invention comprises a method of developing an output
voltage operating independent of temperature, comprising the steps of:
supplying a first current having a predetermined temperature coefficient;
passing said first current through a first transistor and a first resistor, said first
transistor having a temperature coefficient across the base-emitter junction thereof;
and
developing a potential across said first resistor having a temperature coefficient
opposing said temperature coefficient across the base-emitter junction of said first
transistor for substantially cancelling temperature induced variation in the output
voltage.
[0009] In another aspect of the present invention, there is provided a circuit for providing
a reference signal at an output, comprising:
a first transistor having a collector, a base and an emitter, said base being coupled
to the output of the circuit;
a first resistor coupled between said emitter of said first transistor and a first
source of operating potential;
a second transistor having a collector, a base and an emitter, said base being coupled
to said base of said first transistor;
a second resistor coupled between said emitter of said second transistor and said
first source of operating potential;
a third transistor having a collector, a base and an emitter, said emitter being coupled
to a second source of operating potential;
a third resistor coupled between said collectors of said second and third transistors;
a fourth transistor having a collector, a base and an emitter, said base being coupled
to said base of said third transistor;
a fourth resistor coupled between said collectors of said first and fourth transistors;
a fifth resistor coupled between said emitter of said fourth transistor and said second
source of operating potential;
first means coupled between said collector of said fourth transistor and said bases
of said third and fourth transistors for providing base drive thereto;
second means coupled between said collector of said third transistor and said bases
of said first and second transistors for maintaining the potential developed at said
bases of said first and second transistors independent of the potential applied at
said first source of operating potential; and
third means for starting the operation of the circuit.
Brief Description of the Drawings
[0010]
FIG. 1 is a schematic and block diagram illustrating the preferred embodiment of the
present invention; and
FIG. 2 is a schematic diagram illustrating further detail of the current reference
circuit.
Detailed Description of the Preferred Embodiment
[0011] Referring to FIG. 1, voltage reference circuit 10 is shown comprising current reference
circuit 12 having an output for providing a current reference signal flowing into
the collector of transistor 20. The emitter of transistor 20 is coupled through resistor
22 to power supply conductor 24, operating at ground potential. The collector and
base of transistor 20 are coupled to the base and emitter of transistor 26, respectively,
while the collector of transistor 26 is coupled to power supply conductor 27, typically
operating at a positive potential such as V
CC. An output voltage operating independent of temperature and power supply variation
is provided at output terminal 28 that is the base of transistor 20. In addition,
resistors 30 and 32 are serially coupled between output terminal 28 and power supply
conductor 24 for providing a divider ratio of the output voltage at output 34.
[0012] Further detail of current reference circuit 12 is shown in FIG. 2 including FET transistor
40 operating as a resistor and having a source coupled to power supply conductor 27,
a gate coupled to power supply conductor 24 and a drain coupled to the base and collector
of diode configured transistor 42. The emitter of transistor 42 is coupled to the
collector and base of transistor 44, while the emitter of transistor 44 is coupled
to the base and collector of transistor 46. The emitter of transistor 46 is coupled
to the base and collector of transistor 48, and the emitter of the latter is coupled
to power supply conductor 24 thereby forming a diode stack for developing a voltage
of four base-emitter junction potentials (4V
be′s) at the collector and base of transistor 50. The emitter of transistor 50 is coupled
to the collector of transistor 52, and the emitter of transistor 52 is coupled through
resistor 54 to power supply conductor 27, while the emitter of transistor 56 is coupled
through resistor 58 to power supply conductor 27, and the base and collector of transistor
56 are coupled together to the collector of transistor 60. The emitter of transistor
60 is coupled through diode configured transistor 62 and resistor 64 to power supply
conductor 24, and the base of transistor 60 is coupled to the collector of transistor
66, through capacitor 68 to power supply conductor 24 and through resistor 70 to the
collector of transistor 52. The base of transistor 66 is coupled to the base and collector
of transistor 72, to the base of transistor 74 and to the emitter of transistor 76.
The emitters of transistors 66, 72 and 74 are coupled to power supply conductor 24,
the latter path including resistor 78. The collector and base of transistor 76 are
coupled to power supply conductor 27 and to the collector of transistor 74, respectively,
and the collector of transistor 74 is also coupled through resistor 80 to the collector
of transistor 82, which includes an emitter coupled through resistor 84 to power supply
conductor 27 and a base coupled to the bases of transistors 52 and 56 for developing
a reference potential. The base of transistor 82 is also coupled to the base of transistor
86 which includes an emitter coupled through resistor 88 to power supply conductor
27 and a collector that is the output of current reference circuit 12 for providing
the current reference signal.
[0013] The discussion of voltage reference circuit 10 begins with the operation of current
reference circuit 12 as a positive potential, V
CC, is applied at power supply conductor 27. FET transistor 40 is selected for providing
approximately 100K ohms of resistance between power supply conductor 27 and the top
of the diode stack formed of transistors 42-48 for limiting the current flowing therethrough.
The potential applied at the collector of transistor 52 is thus 3V
be′s above ground potential (4V
be′s less the V
be of transistor 50) which is sufficient to conduct current through resistor 70 and
turn on transistors 60 and 62. The current flowing through transistor 60 reduces the
voltage at the base and collector of transistor 56 turning the latter on and completing
a first conduction path between power supply conductors 27 and 24 through resistor
58, transistors 56, 60 and 62 and resistor 64. The low potential at the base of transistor
56 also turns on transistors 52 and 82 creating a second conduction path through resistor
54, transistor 52, resistor 70 and transistor 66, and a third conduction path through
resistor 84, transistor 82, resistor 80, transistor 74 and resistor 78. Once current
reference circuit 12 is started, the voltage developed at the collector of transistor
52 reverse biases the base-emitter junction of transistor 50 thereby removing transistors
40-50 from consideration.
[0014] The current flowing through the collector-emitter conduction path of transistor 76
supplies the base drive for transistors 66, 72 and 74. This diverts negligible current
from the collector of transistor 74 as the base current is effectively divided by
the forward current gain of transistor 76. Transistor 72 helps maintain a stable V
be across the base-emitter junction of transistor 66 as very little current flows through
the collector-emitter conduction path thereof. Resistors 54, 58 and 84 are matched
(e.g., 2K ohms) for establishing identical V
be's for transistors 52, 56 and 82 and equal currents, say 50 microamps, flowing through
the first, second and third conduction paths defined above. Resistors 70 and 80 are
also matched (e.g., 28K ohms) as are resistors 64 and 78 (e.g., 720 ohms) for providing
equal potentials at the collectors of transistors 52 and 82 and equal potentials at
the collectors of transistors 66 and 74, respectively. That is, the collector voltage
of transistor 74 is the V
be of transistor 76 plus the V
be of transistor 74 plus the current flowing through the third conduction path times
the value of resistor 78, while the collector voltage of transistor 66 is the V
be of transistor 60 plus the V
be of transistor 62 plus the potential developed across resistor 64. It is important
to note that the emitter areas of transistors 62 and 74 are sized larger than the
emitter areas of transistors 60 and 76 and therefore conduct a fraction of the current
density. For example, transistors 62 and 74 may be selected with four times the emitter
area of transistors 60 and 76 and correspondingly conduct one-fourth the current density.
Thus, with the V
be's of transistors 60 and 76 equal, the V
be's of transistor 62 and 74 equal and the potentials developed across resistors 64
and 78 equal, the potentials of the collectors of transistors 66 and 74 are also equal.
[0015] The feedback loop formed of transistors 56, 60 and 62 provides the immunity from
power supply variations. If the voltage applied at power supply conductor 27 falls,
the potential at the emitters of transistors 52, 56 and 82 also drops thereby decreasing
the V
be′s thereof and the current flow through the second and third conduction paths. The
collector voltage of transistors 66 and 74 tends to rise as less potential is developed
across resistors 70 and 80 thereby increasing the V
be of transistor 60, drawing more collector current and reducing the voltage developed
at the collector of transistor 56 which compensates the V
be′s of transistors 52, 56 and 82 re-establishing the nominal current flow through the
second and third conduction paths. Alternately, if the voltage applied at power supply
conductor 27 rises, the potential at the emitters of transistors 52, 56 and 82 increases
the V
be′s thereof and the current flow through the second and third conduction paths. The
collector voltage of transistors 66 and 74 falls as more potential is developed across
resistors 70 and 80, decreasing the V
be of transistor 60 which draws less collector current and increases the collector voltage
of transistor 56 and compensating the V
be′s of transistors 52, 56 and 82 again re-establishing the nominal current flow through
the second and third conduction paths. Capacitor 68 is provided for decoupling the
high frequency components at the base of transistor 60 slowing and stabilizing the
response of the feedback loop. Hence, the potential developed at the bases of transistors
52, 56 and 82 is substantially independent of variation in power supply conductor
27 so as to eliminate the Early voltage effect. Moreover, the base currents of transistors
60 and 76 are equal, and the collector voltage of transistors 52 and 82 are equal
and constant regardless of the supply voltage.
[0016] The reference signal developed at the base of transistors 52, 56 and 82 is determined
by the V
bebe of transistor 82 and the current flowing through the third conduction path times
the value of resistor 84. Since transistors 66 and 74 operate at different current
densities, their V
be′s are dissimilar and a delta V
be is developed across resistor 78 having a positive temperature coefficient. Thus,
the current I
C flowing through resistor 78 may be calculated as follows:
where:
- V66 =
- Vbe of transistor 66
- V74 =
- Vbe of transistor 74
- R78 =
- value of resistor 78
- k =
- Boltzman's constant
- T =
- absolute temperature
- q =
- the electron charge
- IC66 =
- collector current through transistor 66
- IS66 =
- saturation current through transistor 66
- IC74 =
- collector current through transistor 74
- IS74 =
- saturation current through transistor 74
[0017] As stated, the emitter area of transistor 74 is four times (4A) the emitter area
of transistor 66 (1A). By combining terms and dividing out the collector current and
saturation current ratios, equation (1) may be reduced to:
[0018] The current I
C is determined by resistor 78 from equation (2); however, observe that the current
flowing through the first, second and third conduction paths and correspondingly the
reference signal provided at the bases of transistors 52, 56 and 82 is still of function
of temperature. This temperature dependency may be used advantageously as will be
shown.
[0019] Returning to FIG. 1, the value of resistor 88 is matched with resistors 54, 58 and
84 for providing a current reference signal flowing through transistor 86 and transistor
20 and resistor 22 equal to that of the third conduction path, current I
C, and having a similar temperature coefficient and operating independent of the power
supply. The base current for transistor 20 is supplied through the collector-emitter
conduction path of transistor 26 thereby diverting negligible current from the collector
of transistor 20 due to its forward current gain. The temperature and power supply
regulated output voltage provided at output terminal 28 is thus equal to the V
be of transistor 20 plus the value of resistor 22, say 10K ohms, times the current I
C, or approximately 1.18 volts. Resistors 30 and 32 form a conventional voltage divider
circuit for providing a reduced output voltage at output 34. Furthermore, the output
voltage is independent of power supply because the current reference signal provided
by the current reference circuit 12 as shown is also independent of power supply variation.
[0020] For the temperature compensation feature, the goal is balance the negative temperature
coefficient of the V
be of transistor 20, approximately -1.68 mV/°K, against the positive temperature coefficient
of the potential developed across resistor 22. The positive temperature coefficient
as seen in equation (2) in combination with resistor 22, which is fabricated from
the same base material (125 ohms/square) of similar geometries as resistor 78 and
therefore matched with a temperature coefficient of about 688 ppm/°K, substantially
cancels the negative temperature coefficient of transistor 20 thereby providing an
output voltage independent of temperature. The cancellation of the temperature coefficients
between the potential across resistor 22 and the V
be of transistor 20 is further demonstrated as follows. The output voltage provided
at output terminal 28 is given as:
[0021] Taking the derivative with respect to temperature yields:
[0022] Substituting equation (2) into equation (4) produces:
[0023] Since resistors 22 and 78 are fabricated from the same base material and have similar
geometries, it can be shown that:
[0024] Furthermore, a typical value for the temperature coefficient of the V
be of transistor 20 is -1.68 mV/°K. By selecting I
C at 50 microamps, resistor 22 at 10K ohms and resistor 78 at 720 ohms with a nominal
temperature of 300°K, equation (5) reduces to:
[0025] Notably, the temperature coefficient of the output voltage can be made non-zero and
easily controlled with a positive or negative slope by adjusting the values of resistors
78 and 22. For example, by increasing the value of resistor 22, the output voltage
at output terminal 28 will have a positive slope temperature coefficient. Conversely,
the temperature coefficient of the output voltage may have a negative slope by decreasing
the value of resistor 22.
[0026] Hence, what has been described is a novel voltage reference circuit using a current
reference signal flowing through a first transistor and a first resistor, operating
independent of the power supply and having predetermined temperature coefficient for
developing a potential across the first resistor with a positive temperature coefficient
which substantially cancels the negative temperature coefficient of the V
be of the first transistor for providing an output voltage operating independent of
temperature and power supply variation.
1. A voltage reference circuit for providing a voltage at an output, comprising:
current supply means (12) including an output for supplying a current having a predetermined
temperature coefficient;
a first transistor (20) having a collector, a base and an emitter, said collector
being coupled for receiving said current having said predetermined temperature coefficient
from said output of said current supply means, said base being coupled to the output
of the voltage reference circuit, said first transistor having a temperature coefficient
across the base-emitter junction thereof;
circuit means (26) coupled between said collector and base of said first transistor
for supplying base drive thereto; and
a first resistor (22) coupled between said emitter of said first transistor and a
first source of operating potential for conducting said current having said predetermined
temperature coefficient which develops a potential across said first resistor with
a temperature coefficient opposing said temperature coefficient across the base-emitter
junction of said first transistor.
2. The voltage reference circuit of claim 1 wherein said circuit means includes a second
transistor (26) having a collector, a base and an emitter, said base being coupled
to said collector of said first transistor, said emitter being coupled to said base
of said first transistor, said collector being coupled to a second source of operating
potential.
3. The voltage reference circuit of claim 2 wherein said current supply means comprises:
third means (40-84) for providing a reference signal at an output;
a third transistor (86) having a collector, a base and an emitter, said base being
responsive to said reference signal, said collector being coupled to said collector
of said first transistor; and
a second resistor (88) coupled between said emitter of said third transistor and said
second source operating potential.
4. The voltage reference circuit of claim 1 wherein the current supply means (12) comprises:
a first transistor (82) having a collector, a base and an emitter, said base being
coupled to the output of the current supply means (12);
a first resistor (84) coupled between said emitter of said first transistor and a
first source of operating potential (27);
a second transistor (52) having a collector, a base and an emitter, said base being
coupled to said base of said first transistor;
a second resistor (54) coupled between said emitter of said second transistor and
said first source of operating potential;
a third transistor (66) having a collector, a base and an emitter, said emitter being
coupled to a second source of operating potential (24);
a third resistor (70) coupled between said collectors of said second and third transistors;
a fourth transistor (74) having a collector, a base and an emitter, said base being
coupled to said base of said third transistor;
a fourth resistor (80) coupled between said collectors of said first and fourth transistors;
a fifth resistor (78) coupled between said emitter of said fourth transistor and said
second source of operating potential;
first means (72, 76) coupled between said collector of said fourth transistor and
said bases of said third and fourth transistors for providing base drive thereto;
second means (56-68) coupled between said collector of said third transistor and said
bases of said first and second transistors for maintaining the potential developed
at said bases of said first and second transistors independent of the potential applied
at said first source of operating potential; and
third means (40-50) for starting the operation of the circuit.
5. The voltage reference circuit of claim 4 wherein said first means includes:
a fifth transistor (76) having a collector, a base and an emitter, said base being
coupled to said collector of said fourth transistor, said collector being coupled
to said first source of operating potential, said emitter being coupled to said bases
of said third and fourth transistors; and
a sixth transistor (72) having a collector, a base and an emitter, said base and collector
being coupled together to said base of said third transistor, said emitter being coupled
to said second source of operating potential.
6. A method of developing an output voltage operating independent of temperature, comprising
the steps of:
supplying a first current having a predetermined temperature coefficient;
passing said first current through a first transistor (20) and a first resistor (22),
said first transistor having a temperature coefficient across the base-emitter junction
thereof; and
developing a potential across said first resistor having a temperature coefficient
opposing said temperature coefficient across the base-emitter junction of said first
transistor for substantially cancelling temperature induced variation in the output
voltage.
1. Spannungsreferenzschaltung, die eine Spannung an einem Ausgang bereitstellt, umfassend:
eine Stromversorgungseinrichtung (12) mit einem Ausgang zum Liefern eines Stromes
mit einem vorbestimmten Temperaturkoeffizienten;
einen ersten Transistor (20) mit einem Kollektor, einer Basis und einem Emitter, wobei
der Kollektor geschaltet ist, den Strom mit dem vorbestimmten Temperaturkoeffizienten
von dem Ausgang der Stromversorgungseinrichtung zu empfangen, und die Basis mit dem
Ausgang der Spannungsreferenzschaltung verbunden ist, wobei der erste Transistor über
seinem Basis-Emitter-übergang einen Temperaturkoeffizienten aufweist;
eine Schaltungseinrichtung (26), die zwischen den Kollektor und die Basis des ersten
Transistors geschaltet ist, um einen Basisantrieb dafür zu liefern, und
einen ersten Widerstand (22), der zwischen den Emitter des ersten Transistors und
eine erste Betriebspotentialquelle geschaltet ist und den Strom mit dem vorbestimmten
Temperaturkoeffizienten leitet, der über dem ersten Widerstand ein Potential mit einem
Temperaturkoeffizienten entwickelt, der dem Temperaturkoeffizienten über dem Basis-Emitter-Übergang
des ersten Transistors entgegengesetzt ist.
2. Spannungsreferenzschaltung nach Anspruch 1, bei der die Schaltungseinrichtung einen
zweiten Transistor (26) mit einem Kollektor, einer Basis und einem Emitter umfaßt,
wobei die Basis mit dem Kollektor des ersten Transistors verbunden ist, der Emitter
mit der Basis des ersten Transistors verbunden ist und der Kollektor mit einer zweiten
Betriebspotentialquelle verbunden ist.
3. Spannungsreferenzschaltung nach Anspruch 2, bei der die Stromversorgungseinrichtung
umfaßt:
eine dritte Einrichtung (40-84), die an einem Ausgang ein Referenzsignal bereitstellt;
einen dritten Transistor (86) mit einem Kollektor, einer Basis und einem Emitter,
wobei die Basis auf das Referenzsignal anspricht und der Kollektor mit dem Kollektor
des ersten Transistors verbunden ist, und
einen zweiten Widerstand (88) der zwischen den Emitter des dritten Transistors und
die zweite Betriebspotentialquelle geschaltet ist.
4. Spannungsreferenzschaltung nach Anspruch 1, bei dem die Stromversorgungseinrichtung
(12) umfaßt:
einen ersten Transistor (82) mit einem Kollektor, einer Basis und einem Emitter, wobei
die Basis mit dem Ausgang der Stromversorgungseinrichtung (12) verbunden ist;
einen ersten Widerstand (84), der zwischen den Emitter des ersten Transistors und
eine erste Betriebspotentialquelle (27) geschaltet ist;
einen zweiten Transistor (52) mit einem Kollektor, einer Basis und einem Emitter,
wobei die Basis mit der Basis des ersten Transistors verbunden ist;
einen zweiten Widerstand (54), der zwischen den Emitter des zweiten Transistors und
die erste Betriebspotentialquelle geschaltet ist;
einen dritten Transistor (66) mit einem Kollektor, einer Basis und einem Emitter,
wobei der Emitter mit einer zweiten Betriebspotentialquelle (24) verbunden ist;
einen dritten Widerstand (70), der zwischen die Kollektoren des zweiten und dritten
Transistors geschaltet ist;
einen vierten Transistor (74) mit einem Kollektor, einer Basis und einem Emitter,
wobei die Basis mit der Basis des dritten Transistors verbunden ist;
einen vierten Widerstand (80), der zwischen die Kollektoren des ersten und vierten
Transistors geschaltet ist;
einen fünften Widerstand (78), der zwischen den Emitter des vierten Transistors und
die zweite Betriebspotentialquelle geschaltet ist;
eine erste Einrichtung (72, 76). die zwischen den Kollektor des vierten Transistors
und die Basen des dritten und vierten Transistors geschaltet ist und einen Basisantrieb
dafür liefert;
eine zweite Einrichtung (56-68), die zwischen den Kollektor des dritten Transistors
und die Basen des ersten und zweiten Transistors geschaltet ist und das an den Basen
des ersten und zweiten Transistors hervorgebrachte Potential unabhängig von dem an
die erste Betriebspotentialquelle angelegten Potential aufrechterhält, und
eine dritte Einrichtung (40-50), die den Betrieb der Schaltung startet.
5. Spannungsreferenzschaltung nach Anspruch 4, bei der die erste Einrichtung umfaßt:
einen fünften Transistor (76) mit einem Kollektor, einer Basis und einem Emitter,
wobei die Basis mit dem Kollektor des vierten Transistors verbunden ist, der Kollektor
mit der ersten Betriebspotentialquelle verbunden ist und der Emitter mit den Basen
des dritten und vierten Transistors verbunden ist, und
einen sechsten Transistor (72) mit einem Kollektor, einer Basis und einem Emitter,
wobei die Basis und der Kollektor zusammen mit der Basis des dritten Transistors verbunden
sind und der Emitter mit der zweiten Betriebspotentialquelle verbunden ist.
6. Verfahren zum Hervorbringen einer Ausgangsspannung, die unabhängig von der Temperatur
arbeitet, wobei das Verfahren die Schritte umfaßt:
Liefern eines ersten Stromes mit einem vorbestimmtem Temperaturkoeffizienten;
Führen des ersten Stromes durch einen ersten Transistor (20) und einen ersten Widerstand
(22), wobei der erste Transistor über seinem Basis-Emitter-Übergang einen Temperaturkoeffizienten
aufweist, und
Hervorbringen eines Potentials über dem ersten Widerstand mit einem Temperaturkoeffizienten,
der dem Temperaturkoeffizienten über dem Basis-Emitter-Übergang des ersten Transistors
entgegengesetzt ist, um die temperaturbewirkte Änderung in der Ausgangsspannung im
wesentlichen aufzuheben.
1. Circuit de référence de tension pour fournir une tension sur une sortie, comprenant
:
un moyen de fourniture de courant (12) comprenant une sortie pour fournir un courant
ayant un coefficient de température prédéterminé ;
un premier transistor (20) ayant un collecteur, une base et un émetteur, ledit collecteur
étant couplé pour recevoir ledit courant ayant ledit coefficient de température prédéterminé
à partir de ladite sortie dudit moyen de fourniture de courant, ladite base étant
couplée à la sortie du circuit de référence de tension, ledit premier transistor ayant
un coefficient de température a travers la jonction base-émetteur de celui-ci ;
un moyen de circuit (26) couplé entre ledit collecteur et la base dudit premier transistor
pour fournir une commande de base à celui-ci ; et
une première résistance (22) couplée entre ledit émetteur dudit premier transistor
et une première source d'un potentiel de fonctionnement pour conduire ledit courant
ayant ledit coefficient de température prédéterminé qui développe un potentiel à travers
ladite première résistance avec un coefficient de température opposé audit coefficient
de température à travers la jonction base-émetteur dudit premier transistor.
2. Circuit de référence de tension selon la revendication 1, dans lequel ledit moyen
de circuit comprend un second transistor (26) ayant un collecteur, une base et un
émetteur, ladite base étant couplée audit collecteur dudit premier transistor, ledit
émetteur étant couplé à ladite base dudit premier transistor, ledit collecteur étant
couplé à une seconde source de potentiel de fonctionnement.
3. Circuit de référence de tension selon la revendication 2, dans lequel ledit moyen
de fourniture de courant comprend :
un troisième moyen (40-84) pour fournir un signal de référence sur une sortie ;
un troisième transistor (86) ayant un collecteur, une base et un émetteur, ladite
base étant sensible audit signal de référence, ledit collecteur étant couplé audit
collecteur dudit premier transistor ; et
une seconde résistance (88) couplée entre ledit émetteur dudit troisième transistor
et ledit second potentiel de source de fonctionnement.
4. Circuit de référence de tension selon la revendication 1, dans lequel le moyen de
fourniture de courant (12) comprend :
un premier transistor (82) ayant un collecteur, une base et un émetteur, ladite base
étant couplée à la sortie dudit moyen de fourniture de courant (12) ;
une première résistance (84) couplée entre ledit émetteur dudit premier transistor
et une première source de potentiel de fonctionnement (27) ;
un second transistor (52) ayant un collecteur, une base et un émetteur, ladite base
étant couplée à ladite base dudit premier transistor ;
une seconde résistance (54) couplée entre ledit émetteur dudit second transistor et
ladite première source de potentiel de fonctionnement ;
un troisième transistor (66) ayant un collecteur, une base et un émetteur, ledit émetteur
étant couplé à une seconde source de potentiel de fonctionnement (24) ;
une troisième résistance (70) couplée entre lesdits collecteurs desdits second et
troisième transistors ;
un quatrième transistor (74) ayant un collecteur, une base et un émetteur, ladite
base étant couplée à ladite base dudit troisième transistor ;
une quatrième résistance (80) couplée entre lesdits collecteurs desdits premier et
quatrième transistors ;
une cinquième résistance (78) couplée entre ledit émetteur dudit quatrième transistor
et ladite seconde source de potentiel de fonctionnement ;
un premier moyen (72, 76) couplé entre ledit collecteur dudit quatrième transistor
et lesdites bases desdites troisième et quatrième transistors pour fournir une commande
de base à celui-ci ;
un second moyen (56-68) couplé entre ledit collecteur dudit troisième transistor et
lesdites bases desdits premier et second transistors pour maintenir le potentiel développé
sur lesdites bases desdits premier et second transistors indépendant du potentiel
appliqué à ladite première source de potentiel de fonctionnement ; et
un troisième moyen (40-50) pour commencer le fonctionnement du circuit.
5. Circuit de référence de tension selon la revendication 4, dans lequel ledit premier
moyen comprend :
un cinquième transistor (76) ayant un collecteur, une base et un émetteur, ladite
base étant couplée audit collecteur dudit quatrième transistor, ledit collecteur étant
couplé à ladite première source de potentiel de fonctionnement, ledit émetteur étant
couplé auxdites bases desdits troisième et quatrième transistors ; et
un sixième transistor (72) ayant un collecteur, une base et un émetteur, ladite base
et ledit collecteur étant couplés ensemble à ladite base dudit troisième transistor,
ledit émetteur étant couplé à ladite seconde source de potentiel de fonctionnement.
6. Procédé de développement d'une tension de sortie fonctionnant indépendamment de la
température, comprenant les étapes de :
fourniture d'un premier courant ayant un coefficient de température prédéterminé ;
passage dudit premier courant à travers un premier transistor (20) et une première
résistance (22), ledit premier transistor ayant un coefficient de température à travers
la jonction base-émetteur de celui-ci ; et
développement d'un potentiel à travers ladite première résistance ayant un coefficient
de température opposé audit coefficient de température à travers la jonction base-émetteur
dudit premier transistor pour annuler substantiellement une variation induite par
la température dans la tension série.